A Study on the Structure of Qajar Period’s Kārbandies (Rasmibandies)

In Iranian architecture, rasmibandi or kārbandi is a geometric structure seen in many Iranian ceilings made up of intersections of similar arches under geometry and mathematical orders. In theoretical geometry, the lowest voussoirs of all arches are situated on circumference of a virtual vertical circle with the same distances. Then in architectural plan we will see a symmetrical arrangement of chords in a circle. Each chord is a plan of a complete arch, almost always a pointed arch. In practical geometry, some arches or all of them will be constructed as ribbed vaults with load bearing ability. Due to rectangle, square and polygonal plan of Persian architecture, some ribs should be trimmed and some remain prefect. This roofing-ceiling system is similar to star patterns of Islamic- Iranian geometrical ornaments. The genuine ones are load bearing roofs which can withstand with no need of hanging from an upper stronger roof. Although in some cases rasmibandies are diminished to an ornamental secondary ceiling with a prefect geometrical essence, unlike muqarnas and yazdibandi ornaments, rasmibandi has an important structural aspect. The structural aspect of it is unseen and not researched. The relation between a plan of rasmibandi and a structure that must adapt it is not clear. Another problem is forces and tensions paths and that the ribs or surfaces are bearing more or less. The oldest sample of this ornamental element known is located in the Atiq Mosque, Shiraz, built in 9th/15th century. Other samples could be found in Na’in Jāme’ Mosque, Cordoba Jāme’ Mosque and Akhpat Monastery from 10th century. Some centuries later, this architectural element can be found only within the Iran’s territory. Even if samples can be seen outside Iran, they are very rare. Therefore, it could be claimed that Iran is considered the origin of kārbandi. From the early Islamic era till Qajar period some evolution occurred in all aspects of kārbani so that it developed for practical use in most Iranian buildings. It has been expanded and used for ceilings in mosques, mausoleums, tombs, bazaars, houses, madrasas, etc. In this article, geometry of rasmibandi has been discussed at first. Its typology is explained based on former papers of authors and scholars. Then, the evolution of its geometry and structure from early times till Qajar period has been surveyed. This study shows that both geometry and structure of rasmibandi reached their climax in Qajar era. This fact is proved by numerous rasmibandies of that era and the complexity of their geometry and precision of structures in comparison to the older ones. Although very complete rasmibandies have remained from the first Isfahan school of architecture period, i.e. Timurid and Safavid time, but the second Isfahan school of architecture, i.e. Qajar period, is the time for more evolution. Similar to the first Isfahan era, the ornamental rasmibandies with no strong load bearing structure are repeated in the second school. At the last part of this article structural behavior of rasmibandi has been investigated via a structural simulation. This simulation shows in a 10-meter span a kārbandi roofing that has low weight in comparison to other masonry vault and domes. It means that material has been used in a more optimal way.